Outdoor Thermometers

When we moved into the new house I bought a great big inexpensive outdoor thermometer and mounted it on the deck. It went up and down with the temperature until this most recent cold snap.

When it got icy & frozen a couple days before Xmas, the needle never dropped below 40º. When it snowed a couple inches on Xmas Eve, the needle never dropped below 40º.

Damn, I thought. The needle done broke.

So I bought another cheapass thermometer & hung it in the same place, while the temperature was still in the lower 30s. Needle never moved below 40º.

Damn!

I stuck the thermometer in my chest freezer. Couple minutes later the needle registered 0º (or more accurately, about 4º). Stuck the OLD thermometer in the freezer. It registered 4º. Double damn!

So okay, hanging the thing on the wall apparently isn't a good idea. It must pick up just enough warmth from the house -- it's not really in any direct sunlight -- to never go below 40º. You'd think an "outdoor thermometer" would be designed to measure the outdoor temperature, not the temperature of the structure on which it is mounted.

What's a guy to do? Hang it on a deck post? Buy a more expensive thermometer?

The only surprising thing I see is that you got two thermometers that showed the exact same temperature. An error of two to four degrees is normal.

You're right that being on the wall is a problem. Also the deck could be reflecting heat. For accuracy, you need to get the thermometer twenty or thirty feet from the house and five to ten feet off the ground. In the shade, but not in the wind if possible.

Quote :

You'd think an "outdoor thermometer" would be designed to measure the outdoor temperature...

The only difference between an indoor and an outdoor thermometer is that an outdoor model should be weatherproofed. It measures the temperature where it is; it's that simple. You wouldn't complain about an indoor thermometer being inaccurate if you hung it in front of a heat vent, would you?

Okay. Everything I have read may be crap - at least the bit about moving away from the house.

I have two temperature sensors set up (not thermometers). One is attached to the house wall, just below the upper deck. The other one is about twenty feet from the house and virtually unrestricted. I just set up the new one which is farther from the house. I have been watching the readings for a few hours, and there is very little difference in the temperature readings. Right now one of them shows 51℉ and the other shows 51.1℉. Checking the wind chill factor, one shows 46.5℉ and the other shows 46℉. It should be noted that only one of the systems reports in tenths; the other is always whole numbers.

I would have expected a sizeable difference in the readings. Maybe I will see bigger differences in the mornings, or when the weather gets disgustingly hot.

The only real difference I see is that the displays also show inside temperature, and the newer one seems to be about two degrees high.

The one against my house was accurate at 51º too. It was only when temps dipped below 40º that the thermometer stopped reading accurately.

The little thermocouple -- a spiral of temperature-sensitive metal on the back of the unit, connected to the needle on the front -- no fancypants digital for ME! -- sits between the thermometer front and the outside wall. I'm guessing this little air pocket never got below 40º.

If I mounted it on one of the 4x4s on the deck, it would be vulnerable to wind (hangs on a single nail/screw).

If I mounted it on a tree, it might also be blown down.

If I hung it from a chain, it would swing in the wind which might not be good for its longevity.

Sigh. I guess maybe my best option is to buy a new slightly-more-expensive digital thermo ($24 instead of $12) and hang the sending unit on the deck rail and the wireless receiver inside the kitchen.

Or maybe hang the analog on the side of my (unheated) toolshed -- but then I couldn't see it easily.

Both of the thermometers showed 40 degrees. Are you one hundred percent positive that the temperature wasn't forty degrees? And don't go by the snow: snow can sometimes stay on the ground for a long time in the high thirties.

Try hanging one of the thermometers on the old spot on the house and the other one in an open area. See if they measure the same when it gets cold.

I use an expensive chef's thermometer for checking the accuracy of cheaper thermometers.

My dad, ever the gizmo freak, had an earlier non-digital version on his house. Wind speed & direction, barometer, humidity, current temp, high and low temp this month, high and low temp this year, provisions for charting out a history of all this.

As a well-known gadget lover, I have been given two weather stations as gifts over a period of under ten years. I don't know why she thought I would want one (I had never given it a thought), but as long as I have them, I will try to get as much use from them as I can (not much, really).

Kind of fun, actually. I just noticed the new system, which has a running ticker on the bottom of the display, has just predicted rain. On the old system, I had to enter the barometric pressure as a reference. The new one "learns" the normal pressure. The instructions say it takes about two weeks, and there is a "Learning" icon displayed. I wonder how they do that.

If all you are interested in is the current temperature, you have no need of a thermometer. For current temp, there are only five possibilities: "Nice," "Kind of warm," Hotter than hell," "Oooh, chilly," and "Cold as a witch's tit." These are immediately discernible by simply stepping outside. And it's free!

I have a similar one. When I started having problems with the one I had, my wife bought me another one.

The new one has the external bits on the southeast side of the house. The old one - which still works except for the rain gauge - is on the northwest side of the house. It's fun to watch the temperature readings. In the morning, it's much warmer on the southeast (where the sun is coming up). As the day goes on, the difference between the two temperature readings moves with the sun until it is reading warmer on the northwest side.